You might check your hygrometer's calibration. Even though it can be harder in a dry climate to maintain the humidor, ambient RH shouldn't affect the cigars; it's the RH inside the humidor that matters. I live in a very dry climate and like to keep my humidor at 60-65 percent. Any more than that and my cigars don't burn evenly and have a harder draw and occasional split wrapper issues.
Anyhow, your hygrometer might be lying to you. They can be as much as 10-15% off. It's not a big deal as long as you can use the hygrometer to put your cigars where you like them RH-wise but the calibration can be checked:
salt test